In the central nervous system of a mammal, neural stem cells exist through the entire life of the individual and contribute to the growth and homeostasis of the central nervous system by producing a variety of neurons and glia. Techniques that have recently been developed aiming at the isolation and culturing of neural stem cells from the brain of mammals, including humans, are expected to provide potential applications to the cell transplant therapies for various types of neurodegenerative diseases and injures. No appreciable achievement is still reported, however, despite some attempts exerted to obtain, from the neural stem cells cultured and amplified in vitro, different types of neurons that can be generated and differentiated from stem cells under control of diversified endogenous and exogenous factors, espeGially motor neurons that can be specifically generated at the initial stage of embryogenesis.
Accordingly, an object of the present invention is to provide means for efficiently inducing differentiation of ES cells, which have the capacity to differentiate into any type of mature cells in an individual, into neural stem cells maintaining properties of those cells in the early stage of development. Another object of the present invention is to provide a technique for selectively producing a specific type of neuron, such as motor neurons, from the neural stem cells.